28 M. de Quatrefages on the Organization of 



be much more intense and brilliant in places where the fresh 

 water dripped or trickled over the rocks than where they were 

 comparatively dry. In the first of these the crust was of " a dark 

 blood-colour/' in the last " a brick-red." But among the former 

 he observed some patches which were " a bright orange." This 

 he attributed to a fuller state of fructification, but neglected to 

 put up specimens. It may, however, be doubted whether this 

 last colour did not originate in an excess of fresh water, which 

 we know changes to orange the red of many Floridece, as parti- 

 cularly observed in Nitophyllum versicolor. 



Probably this production is common in similar situations on 

 other of the British coasts, but, with numerous others of the 

 crustaceous class of Algse (a neglected group, which will repay in 

 novelty an observer who has patience to look for them), has been 

 hitherto unnoticed or passed by. Though our information re- 

 specting it is still imperfect, its characters are such as to exclude 

 it from any established genus with which I am acquainted. The 

 brilliant red colour and substance sever it from Ralfsia, Berk. 

 (Padina ? deusta, Hook.), which in habit it more nearly resembles 

 than any other British plant ; but this is a resemblance of habit 

 alone, and therefore more one of analogy than affinity. With 

 the Mediterranean Peysonellia it has, seemingly, more affinity, 

 and it is in the neighbourhood of that genus that I propose, for 

 the present at least, to place it. W. H. H. 



EXPLANATION OF PLATE II. 



Fig. 1 . Bhododermis Drummondii, natural size. 

 Fig. 2. Portion near the margin, magnified. 

 Figs. 3 and 4. Different views of tubercles. 

 Fig. 5. Portion of the surface highly magnified. 



X. — Researches on the Organization of the Invertebrate Animals 

 of the Western Coast of France. By M. de Quatrefages. 

 Communicated by Alfred Tulk, M.B.C.S. 



The admirable report of M. Milne Edwards upon this subject, 

 to which want of space in a recent number of this Journal ad- 

 mitted only of briefly directing the attention of the reader, con- 

 tains amongst others a most valuable series of observations by 

 M. Quatrefages relative to the organization of certain Gasteropoda, 

 which have hitherto been incorrectly associated with the genus 

 Doris under the general title of Nudibranchiata, but which differ 

 much, through the degradation of their internal structure, from 

 all the ordinary Mollusca. As regards the general form of their 

 body, the generative organs and the position of the central ner- 

 vous ganglia, these animals resemble the other Gasteropoda, 



